Donald Trump’s Take on de Blasio? ‘The Worst Mayor in the U.S.’

Donald J. Trump tore into Mayor Bill de Blasio on Twitter on Friday, accusing New York City’s top elected official of “ineptitude” and calling him “the worst Mayor in the U.S., & probably the worst Mayor in the history of #NYC.”

What took him so long?

Mr. Trump — the real estate mogul and Republican presidential candidate given to dismissing his critics as cowards, liars or worse — has, it turns out, mostly held his tongue about Mr. de Blasio, a liberal Democrat and seemingly ripe target who resides two and a half miles from Trump Tower.

The rebuke on Friday came after Mr. de Blasio, in a radio interview, called Mr. Trump a “blowhard” for supporting police surveillance of mosques.

Mr. Trump, as he often does, responded with a post on Twitter that, three hours later, had been retweeted nearly 1,300 times: “@BilldeBlasio should focus on running #NYC & all of the problems that he has caused with his ineptitude, & not be so focused on me!”

Before that, there was little record of Mr. Trump, a connoisseur of the insult, directing his venom toward the mayor. In fact, in 2013, he predicted that Mr. de Blasio would “end up being a good mayor, maybe a very good mayor.”

This summer, when Mr. de Blasio criticized Mr. Trump’s stance on immigration, and threatened to review the city’s contracts with his affiliated companies, Mr. Trump responded rather formally, with a sternly worded letter to city officials. It was notably lacking in insults.

Some in political circles speculated on Friday that Mr. Trump, as a force in the city’s real estate industry, may have been reluctant to cross a man whose administration is his primary regulator.

“He needs the Buildings Department, he needs the Fire Department, he needs various agencies to approve whatever project he has,” George Arzt, a longtime political consultant, said. “I wouldn’t want to make fun of the mayor for that reason if I was a developer.”

While Mr. Trump’s name is a fixture of the skyline, his personal portfolio in New York is small. Privately, real estate executives said on Friday that he might have been motivated by a desire to protect the interests of his son-in-law, Jared C. Kushner, who is pursuing numerous projects around the city.

Asked about Mr. Trump’s remarks, a spokeswoman, Hope Hicks, said only that they were in response to Mr. de Blasio’s radio comments.

The mayor, for his part, has gleefully criticized prominent Republicans in recent days. He singled out Gov. Chris Christie of New Jersey for his views on Syrian refugees, saying the governor was acting “un-American.” On Friday, referring to the terrorist group that staged the deadly attacks in Paris last week, Mr. de Blasio said that Mr. Trump was “saying things that, bluntly, play right into ISIS’ hands.”

Roger J. Stone Jr., a Republican consultant and former adviser to Mr. Trump, said he was surprised by the developer’s comments.

“Can’t imagine why Trump would attack de Blasio,” Mr. Stone wrote in an email. “De Blasio not well known (and therefore not yet hated) around the country.”

A version of this article appears in print on , on Page A16 of the New York edition with the headline: Trump’s Take on de Blasio? ‘The Worst Mayor in the U.S.’ . Order Reprints | Today’s Paper | Subscribe